Trailing arm suspension devices are widely used as suspension devices for vehicles. Torsion beam suspension devices in which right and left trailing arms are connected by a cross beam (also called “torsion beam”) are advantageous in terms of cost, and are used for rear wheels of small cars. A trailing arm suspension device described in Japanese Unexamined Patent Application Publication No. H08-127211 (Patent Literature 1) is known as an example of such trailing arm suspension devices. In the trailing arm suspension device of Patent Literature 1, a spindle for attaching a wheel is provided at the rear end of each trailing arm. This spindle protrudes outward in the lateral direction of a vehicle.
In recent years, many in-wheel motor drive devices have been proposed in which a motor is placed in an inner space region of a road wheel of a wheel to drive the wheel with this motor. For example, suspension devices described in Japanese Unexamined Patent Application Publication Nos. 2010-116017 (Patent Literature 2) and 2006-27310 (Patent Literature 3) are known as suspension devices that include trailing arms and suspend in-wheel motor drive devices. In the suspension device of Patent Literature 2, each in-wheel motor drive device is placed inward of the trailing arm in the lateral direction of a vehicle. In the suspension device of Patent Literature 3, each in-wheel motor drive device is placed outward of the trailing arm in the lateral direction of a vehicle.